Laminating adhesives hardenable by radiation

ABSTRACT

A method of forming a film laminate uses an adhesive composition containing at least three components A, B and C. The method includes providing a radiation curable adhesive that contains a) a compound bearing at least one epoxy group, b) a compound with at least three OH groups and a molecular weight below 400 and c) a photoinitiator which initiates a polymerization of components a) and b) after exposure to light with a wavelength of 100 to 600 nm.

[0001] This invention relates to an adhesive containing three componentsA, B and C for the production of film laminates. Component A of theadhesive contains at least one compound containing at least one epoxygroup, component B contains at least one compound with at least three OHgroups and a molecular weight below 400 and component C contains atleast one photoinitiator which initiates a polymerization of componentsA and B after exposure to light with a wavelength of 100 to 600 nm.

[0002] In the field of adhesives, particularly in the lamination ofweb-form materials, there is an increasing demand for short cure timesand a shorter response time of the adhesives used for lamination.Conventional systems widely available on the market are generally basedon polyurethane, acrylate or epoxy binders which cure by relatively slowcrosslinking through reaction with added hardener or with moisture. Theusual cure time for commercially available systems such as these isabout 4 to about 21 days. However, a cure time as long as this toachieve maximal strength of the film laminates is generally notdesirable.

[0003] Film laminates are exposed in their production, processing anduse to a number of stresses which, typically, do not occur with otherbonded materials or do not occur to the same extent as they do in filmlaminates. In the production of film laminates, materials partlydiffering in their flexibility and surface structure are bonded to oneanother. They are generally web-form materials of, for example, paper,plastics, plastics coated by vapor deposition with metals or metaloxides, more particularly transition metals oxides, or metal foils, moreparticularly aluminium foils.

[0004] During their production, processing and use, the film laminatesare exposed to a number of mechanical stresses which impose stringentdemands on the mechanical properties of the adhesive establishing thebond between the materials. Since the web-form materials to be bondedare normally materials with high flexibility which are constantlyexposed to tensile and flexural stresses during production, processingand use, the adhesive itself has to possess sufficiently highflexibility to be able to withstand the stresses occurring withoutdamage or failure of the adhesive bond.

[0005] In addition, however, the adhesive is also expected to show highpeel strength to be able to withstand tensile stresses appliedperpendicularly to the laminate surface without separation of the filmlaminate.

[0006] In addition, the adhesive is also generally expected to satisfyvarious criteria in regard to crystallization behavior and discolorationwhich exceed the performance features of adhesives for conventionalapplications. For example, in the bonding of transparent plastic films,the film laminate is also expected to remain transparent withoutclouding through crystallization of the adhesive. In addition, theadhesive must not have any tendency to form colored secondary products,even in the event of prolonged storage of the film laminate, for exampleunder UV light.

[0007] In addition, film laminates are expected to show high heatresistance after only a short time. This property is particularlyimportant when film laminates are to be used for packaging productswhile they are still hot, for example with a view to shorteningproduction and filling cycles. However, the feature of heat resistanceis also of importance when, for example, materials already at leastpartly wrapped in the film laminate are to be subjected to heating.

[0008] Problems are generally involved in the bonding of films which donot have the transparency required for initiating the polymerizationreaction of the adhesive. If, therefore, the films to be bonded togetherare non-transparent materials, the adhesive-coated film generally has tobe irradiated on the adhesive side before that side is bonded to asecond film. This procedure presupposes that bonding to the second filmtakes place at a time at which polymerization of the adhesive, i.e.curing, is not yet complete. However, the adhesive must be capable ofdeveloping sufficient adhesion even at that time to ensure that thesecond web adheres.

[0009] Whereas radical-polymerizing adhesive systems often cure tooquickly and show inadequate initial adhesion, cationically polymerizingadhesive systems lend themselves to a laminating process in which theadhesive layer applied to the first film is irradiated and the secondfilm is subsequently applied. This is generally attributable to the factthat cationic systems have a slower cure rate than radical-polymerizingadhesive systems. However, another frequent disadvantage of commerciallyavailable systems is that the time which the adhesive bond takes to curecompletely is thus too long for economic application of this bondingtechnique.

[0010] A quality criterion increasing in significance for film laminatesis the substantial absence of “migrates”. Migrates are understood to below molecular weight constituents of the film laminate which, on the onehand, are not immobile within the laminate, i.e. are capable ofmigrating within the laminate, and which on the other hand are capableof diffusing from the laminate into the material wrapped in thelaminate. Since low molecular weight constituents such as these canaffect the physical health of living beings, more particularly humanbeings, there is a need to provide substantially migrate-free filmlaminates.

[0011] DE-U 94 20 640 relates to radiation-curing compositionscontaining OH-terminated polyurethanes, an epoxy compound and aphotoinitiator. The document in question describes a single-stage,radiation-curing adhesive composition which is characterized both byhigh initial adhesion and by high ultimate adhesion when it is used as alaminating adhesive.

[0012] EP-A 0 688 804 describes multicomponent, cationically curingepoxy compositions and a process for curing these compositions. itdescribes cationically curing epoxy compositions in various embodimentswhich generally contain as basic constituents a mixture of compoundsthat form Lewis acids and/or Brönsted acids under irradiation,cationically polymerizable monomers containing epoxy groups and at leastone other constituent selected from the group of flexibilizing agents,retarders, radical-polymerizable monomers, accelerators and modifiers.Alcohols and glycols with a molecular weight of at least 200 to 20,000g/mole are mentioned as flexibilizing agents.

[0013] DE-A 43 40 949 describes cationically curing epoxy compositionsand their use. This document mentions a photoinitiated, cationicallycuring epoxy composition which contains at least one retarder, at leastone accelerator, at least one ferrocenium complex salt and at least onecyclo-aliphatic compound containing epoxy groups together with typicalauxiliaries and additives.

[0014] The adhesives representing the prior art are generally attendedby the disadvantage that they do not satisfy all the requirements whichan adhesive used for the production of film laminates is expected tomeet. Thus, although quick-curing adhesives can be produced from epoxycompounds and polyurethane polyols, their heat resistance is not as goodas it should be, for example, for the preparation of foods or thesterilization of medical instruments.

[0015] Accordingly, the problem addressed by the present invention wasto provide an adhesive system for the production of film laminates whichwould withstand the severe stressing involved in the production,processing and use of such laminates and which would have a fast curetime and high shear and peel strengths. Another problem. addressed bythe invention was to provide an adhesive for the production of filmlaminates with which it would be possible to obtain film laminatescharacterized by high heat resistance and a minimal content of migrates(low molecular weight polyols).

[0016] The problems stated above have been solved by an adhesivecontaining at least three components a, B and C which is described inthe following.

[0017] The present invention relates to the use of an adhesivecontaining at least three components A, B and C for the production offilm laminates,

[0018] a) component A containing a compound bearing at least one epoxygroup,

[0019] b) component B containing a compound with at least three OHgroups and a molecular weight below 400 and

[0020] c) component C containing a photoinitiator which initiates apolymerization of components A and B after exposure to light with awavelength of 100 to 600 nm.

[0021] In a first embodiment of the present invention, an adhesivecontaining components A, B and C is used for the production of the filmlaminates. Component A is at least one compound containing at least oneepoxy group or a mixture of two or more such compounds.

[0022] An “epoxy group” in the context of the present invention is afunctional group which has an oxirane ring. Such epoxy groups can bepolymerized in the presence of cationic initiators by methods known tothe expert. Component A used in accordance with the present inventionmay contain a compound containing at least one epoxy group as soleconstituent, although a mixture of two or more compounds containing atleast one epoxy group may also be used as component A.

[0023] It is sufficient for the synthesis of polymers if the compoundcontaining at least one epoxy group present as part of component Acontains only one epoxy group.. However, it may be desirable—with a viewto obtaining a higher degree of crosslinking in the adhesive film—atleast partly to use one or more compounds containing more than one epoxygroup in the molecule as a constituent of component A. The compoundsused as part of component A in accordance with the present inventionadvantageously contain up to about four epoxy groups per molecule. Inone particularly preferred embodiment, the average epoxy group contentof component A as a whole is about 1 to about 2.5 and, moreparticularly, about 1.5 to about 2.0.

[0024] Basically, a low molecular weight epoxide may be used as thecompound containing at least one epoxy group, although relatively highmolecular weight epoxides or mixtures of low molecular weight andrelatively high molecular weight epoxides may also be used as componentA.

[0025] “Low molecular weight compounds” in the context of the presentinvention are compounds containing at least one epoxy group which have amolecular weight of not more than about 400. Compounds containing atleast one epoxy group and having a molecular weight of more than 400 arecorrespondingly referred to as “relatively high molecular weightcompounds” in the present specification.

[0026] Relatively high molecular weight compounds containing at leastone epoxy group can contain the epoxy group, for example, at the end ofa polymer chain, although the epoxy group may also be attached withinthe polymer backbone or laterally to the polymer backbone. In the caseof compounds containing more than one epoxy group, the correspondingrelatively high molecular weight compound may also contain epoxy groupsin two or more of the described configurations in relation to the mainpolymer chain. Thus, a compound with more than one epoxy group maycontain, for example, one terminal and one lateral epoxy group or oneepoxy group within the polymer backbone and one lateral epoxy group.

[0027] Compounds containing at least one epoxy group suitable for use ascomponent A in accordance with the present invention include, forexample, the cycloaliphatic epoxides. Examples of cycloaliphaticepoxides are bis-(3,4-epoxycyclohexylmethyl)-oxalate,bis-(3,4-epoxycyclohexyl-methyl)-adipate,bis-(3,4-epoxy-6-methylcyclohexylmethyl)-adipate andbis-(3,4-epoxycyclohexylmethyl)-pimelate; mixtures of two or more of thecompounds mentioned may also be used.

[0028] Also suitable are 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylates, for example3,4-epoxycyclohexylmethyl-3,4-epoxycyclo-hexane carboxylic acid,3,4-epoxy-1-methylcyclohexylmethyl-3,4-epoxy-1-methylcyclohexanecarboxylic acid, 6-methyl-3,4-epoxycyclohexylmethyl-6-methyl-3,4-epoxycyclohexane carboxylic acid,3,4-epoxy-2-methylcyclo-hexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylic acid,3,4-epoxy-5-methylcyclohexylmethyl-3,4-epoxy-5-methylcyclohexanecarboxylic acid or the like or mixtures of two or more thereof.

[0029] Other suitable epoxides which may be used in accordance with thepresent invention include glycidyl ethers obtainable, for example, frompolyhydric phenols, for example diglycidyl ethers of2,2′-bis-(2,3-epoxy-propoxyphenol)propane.

[0030] Commercially available compounds containing at least one epoxygroup may also be used with advantage. Examples of such compounds areoctadecylene oxide, epichlorohydrin, styrene oxide, vinyl cyclohexeneoxide, glycidol, glycidyl methacrylate, diglycidyl ethers of bisphenol A(for example EPON 828, EPON 1004 and EPON 1010, products of ShellChemical Co.; DER-331, DER-332 and DER-334, products of Dow ChemicalCo.), vinyl cyclohexene dioxide (for example ERL-4206, a product ofUnion Carbide Corp.), 3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexenecarboxylate (for example ERL-4221, a product of Union Carbide Corp.),3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methyl-cyclohexenecarboxylate (for example ERL-4201, a product of Union Carbide Corp.)bis-(3,4-epoxy-6-methylcyclohexylmethyl)-adipate (for example ERL-4289,a product of Union Carbide Corp.), bis-(2,3-epoxy-cyclopentyl)-ether(for example ERL-0400, a product of Union Carbide Corp.), aliphaticpropylene-glycol-modified epoxy resin (for example ERL-4050 or ERL-4052,products of Union Carbide Corp.), dipentene dioxide (for exampleERL-4269, a product of Union Carbide Corp.), epoxidized polybutadiene(for example OXIRON 2001, a product of FMC Corp.), silicone resincontaining epoxy functionality, flame-retardant epoxy resins (forexample DER-580, a product of Dow Chemical Co.), butane-1,4-dioldiglycidyl ethers of phenol-formaldehyde novolak (for example DEN-431 orDEN-438, products of Dow Chemical Co.) and resorcinol diglycidyl ether(for example KOPOXITE, a product of Koppers Co., Inc.).

[0031] Other suitable compounds containing at least one epoxy group arepolymers containing epoxy groups obtainable, for example, by thepolymerization of ethylenically unsaturated epoxy compounds bearingepoxy groups. Examples of such epoxyfunctional ethylenically unsaturatedcompounds are the acrylates of glycidol, for example glycidyl acrylateor glycidyl methacrylate. These compounds are advantageouslycopolymerized with at least one other ethylenically unsaturated compoundthat does not bear any epoxy groups. Polyurethanes containing epoxygroups, for example, are also suitable. Such polyurethanes areobtainable, for example, by reacting OH-functional polyesters orpolyethers with poly-functional isocyanates, the stoichiometric ratio ofisocyanate groups to OH groups being selected so that the correspondingpolyurethane has at least one free isocyanate group which issubsequently reacted, for example, with 1-hydroxy-2,3-epoxypropane oranother suitable epoxide.

[0032] Component A generally contains up to about 30% by weight andpreferably up to about 10% by weight of a compound containing only oneepoxy group. The percentage content of compounds containing two or moreepoxy groups is up to about 50% by weight and preferably about 10 toabout 40% by weight, the percentage content of epoxides with afunctionality of three or more in component A being up to about 10% byweight.

[0033] Based on the adhesive as a whole, the percentage content ofcomponent A is about 5 to about 60% by weight and preferably about 10 toabout 40% by weight.

[0034] Component B present in the adhesives used in accordance with theinvention contains a compound with at least three OH groups and amolecular weight below 400.

[0035] The percentage content of trifunctional compound, i.e. a compoundcontaining three OH groups, is about 1 to about 10% by weight, based onthe adhesive as a whole.

[0036] Suitable OH-containing compounds are, for example, higheralcohols, such as glycerol, trimethylol propane, pentaerythritol andsugar alcohols, and oligomeric ethers of the individual compoundsmentioned or oligomeric ethers of a mixture of two or more of thecompounds mentioned with one another.

[0037] In addition, the reaction products of low molecular weightpolyhydric alcohols with alkylene oxides containing up to 4 carbon atomsmay be used as the polyol component for producing the polyesters.Suitable reaction products are, for example, reaction products ofpolyhydric alcohols, such as glycerol, trimethylol ethane and/ortrimethylol propane, pentaerythritol or sugar alcohols with the alkyleneoxides mentioned to form oligoether polyols with a molecular weight ofnot more than about 400.

[0038] The adhesive to be used in accordance with the invention containsa photoinitiator or a mixture of two or more photoinitiators ascomponent C. The photoinitiator is capable of initiating thepolymerization of the epoxy groups by exposure to radiation.Photoinitiators which produce Lewis or Brönsted acids under the effectof electromagnetic radiation, more particularly under the effect oflight, are particularly suitable for this purpose.

[0039] According to the invention, complex onium compounds arepreferably used as the photoinitiators which produce Lewis acids and/orBrönsted acids under the effect of light. Basically, any photosensitivearomatic sulfonium or iodonium salts are suitable for the light-inducedinitiation of the polymerization reaction. The trisaryl sulfoniumhexafluoro-antimonates, the trisaryl sulfonium hexafluorophosphatespresent, for example, in the commercial products Cyracure® UVI-6974 andUVI-6990 (products of UCC, Danbury, UK) andbis-(4,4′-dimethylbenzyl)-iodonium tetra-(pentafluorophenyl)-borate (UVCATA 200, a product of Rhone-Poulenc, Saint-Fons, France) areparticularly suitable.

[0040] The photoinitiator used in accordance with the present inventionis capable of initiating a polymerization of component A after exposureto light with a wavelength of about 100 to about 600 nm. In onepreferred embodiment of the invention, the polymerization is initiatedby exposure to light with a wavelength of about 150 to about 500 nm, forexample in the range from about 200 to about 480 nm.

[0041] The adhesive to be used in accordance with the invention maycontain a compound with a least two OH groups and a molecular weight ofat least 400 or a mixture of two or more such compounds as component D.

[0042] Compounds suitable for use as component D are, for example,polyester polyols, polyether polyols, polyurethane polyols,polycarbonate polyols, polyvinyl acetyl polyols, polyacrylate polyols,polymethacrylate polyols or copolymers of suitable acrylate salts andmethacrylates or mixtures of two or more of the polyols mentioned.

[0043] The compounds used as component D have a molecular weight ofpreferably more than about 400 to about 10,000 and, more preferably,more than about 400 to about 2000.

[0044] According to the invention, polyester polyols, polyether polyolsand polyurethane polyols are particularly preferred as component D.

[0045] The polyester polyols. suitable as component D are preferablypolyesters with a molecular weight (M_(n)) of more than about 400 toabout 10,000. Preferred polyester polyols are prepared, for example, byreaction of low molecular weight alcohols, more particularly ethyleneglycol, diethylene glycol, neopentyl glycol, hexanediol, butanediol,propylene glycol, glycerol or trimethylol propane, by polycondensationwith a poly-carboxylic acid or a mixture of two or more such acids. Forexample, dihydric and/or trihydric alcohols may be condensed withdicarboxylic acids and/or tricarboxylic acids or reactive derivativesthereof to form polyesters. Suitable dicarboxylic acids are, forexample, succinic acid and higher homologs thereof containing up to 16carbon atoms, unsaturated dicarboxylic acids, such as maleic acid orfumaric acid, an aromatic dicarboxylic acids, more particularly theisomeric phthalic acids, such as phthalic acid, isophthalic acid orterephthalic acid. Suitable tricarboxylic acids are, for example, citricacid and trimellitic acid. Also suitable are aliphatic polycarboxylicacids, such as adipic acid, glutamic acid, pimelic acid, aromatic acids,such as naphthalene dicarboxylic acid, cycloalkyl acids, such ascyclohexane dicarboxylic acid, or acids containing hetero atoms, such asS or N, for example diglycolic acid, ethylether-2,2-dicar-boxylic acidor thiodiglycolic acid.

[0046] Other polyols suitable for the production of the polyesters arealiphatic alcohols containing two to four OH groups per molecule. The OHgroups are preferably primary, but may also be secondary. Suitablealiphatic alcohols include, for example, ethylene glycol, propyleneglycol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol,heptane-1,7-diol, octane-1,8-diol and higher homologs and isomersthereof which can be obtained by the expert by extension of thehydrocarbon chain by one CH₂ group at a time or by introduction ofbranches into the carbon chain. Also suitable are higher alcohols, forexample glycerol, trimethylol propane, pentaerythritol and oligomericethers of the substances mentioned either as such or in the form ofmixtures of two or more of the ethers mentioned with one another.

[0047] In addition, the reaction products of low molecular weightpolyhydric alcohols with alkylene oxides containing up to 4 carbon atomsmay also be used as the polyol component for producing the polyesters.Suitable reaction products are, for example, reaction products ofethylene glycol, propylene glycol, the isomeric butane diols or hexanediols with ethylene oxide, propylene oxide and/or butylene oxide. Thereaction products of polyhydric alcohols, such as glycerol, trimethylolethane and/or trimethylol propane, pentaerythritol, or sugar alcoholswith the alkylene oxides mentioned to form polyether polyols are alsosuitable. In addition, the reaction products of low molecular weightpolyhydric alcohols with alkylene oxides containing up to 4 carbon atomsmay also be used as the polyol component for producing the polyesters.Suitable reaction products are, for example, reaction products ofethylene glycol, propylene glycol, the isomeric butane diols or hexanediols, with ethylene oxide, propylene oxide and/or butylene oxide. Thereaction products of polyhydric alcohols, such as glycerol, trimethylolethane and/or trimethylol propane, pentaerythritol or sugar alcohols,with the alkylene oxides mentioned to form polyether polyols are alsosuitable. Particularly suitable polyols for producing the polyesters arepolyether polyols with a molecular weight of about 100 to 5000 andpreferably in the range from about 200 to about 3000. Propylene glycolwith a molecular weight of about 300 to about 2500 is most particularlypreferred for the purposes of the present invention. Polyether polyolsobtained, for example, by the polymerization of tetrahydrofuran are alsosuitable.

[0048] A group of polymers preferably used as component D in accordancewith the present invention are the polyurethane polyols. In the contextof the present invention, polyurethane polyols are understood to becompounds obtainable by polyaddition of dihydric and/or higher alcoholsand polyisocyanates. Polyesters and/or polyethers with a molecularweight of about 300 to 10,000 and preferably in the range from about 800to about 5000 containing at least two hydroxy groups are typicallyselected as polyols for the production of the polyurethanes. Polyesterssuitable for the production of the polyurethanes usable in accordancewith the present invention are any OH-terminated polyesters which can bechain-extended by reaction with an at least difunctional isocyanate.These include, for example, the polyesters mentioned above.

[0049] Other dihydroxy compounds which may be used for the preparationof the polyesters suitable for use as polyol component for producing thepolyurethanes are, for example, butane-1,3-diol, butane-1,4-diol,butane-2,3-diol, 2,2-diethylpropane-1,3-diol,2-methyl-2-propylpropane-1,3-diol, isomeric octane diols, ethylenicallyunsaturated difunctional compounds, such as heptene diol, octene diol,and difunctional compounds containing N or S hetero atoms, for examplediethylene glycol, triethylene glycol, thio-ethylene glycol,diethanolamine or N-methyl diethanolamine or mixtures of two or morethereof.

[0050] To produce the polyurethanes, the diols are generally reactedwith corresponding, at least difunctional isocyanates. The isocyanatesused in accordance with the present invention may be aliphatic oraromatic and may contain about 4 to about 40 carbon atoms. Examples ofsuitable isocyanates are hexamethylene diisocyanate (HDI), 1,8-octanediisocyanate, 1,10-decane diisocyanate, diisocyanates obtainable, forexample, from the dimerization of fatty acids and correspondingsubsequent functionalization, 1,4-phenylene diisocyanate, tetramethylxylylene diisocyanate (TMXDI), 2,4- and 2,6-toluene diisocyanate andmixtures thereof, 1,5-naphthylene diisocyanate, 2,4′- or 4,4′-diphenylmethane diisocyanate (MDI) and mixtures thereof, isophorone diisocyanate(IPDI), cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and-1,4-diisocyanate, 2,4- and 2,6-hexahydrotoluene diisocyanate,hexahydro-1,3- or -1,4-phenylene diisocyanate, 2,2′-diphenyl methanediisocyanate or 4,4′-diphenyl methane diisocyanate or mixtures of two ormore of the diisocyanates mentioned. Other suitable isocyanates forproducing the polyurethane present in component A are trifunctional orhigher polyisocyanates obtainable, for example, by oligomerization ofdiisocyanates. Examples of such trifunctional and higher polyisocyanatesare the triisocyanurates of HDI or IPDI or mixed triisocyanuratesthereof.

[0051] In general, the average molecular weight of the polymers used ascomponent D should not be any lower than 400. Since polymers generallyhave a statistical molecular weight distribution depending on theparticular method selected for their synthesis, the expression “averagemolecular weight” relates to the number average (M_(n)) of the molecularweight of the polymers present in component A. This allows for the factthat individual polymeric molecules of which the molecular weight isbelow the value of 400 mentioned may also be present.

[0052] In addition to components A, B and C and optionally D, theadhesive to be used in accordance with the invention may also containanother component E. Component E contains at least one compound or amixture of two or more compounds containing a cationically polymerizablefunctional group which is not an epoxy group. Examples of such compoundsare olefins, vinyl ethers, vinyl arenes, more particularly styrene, andheterocyclic compounds, such as ethers, thioethers, esters or acetals.Vinyl ethers formally obtainable, for example, from the etherificationof alcohols, preferably polyols, and vinyl ethers (in fact acetylene isgenerally used as starting material in the industrial production of thevinyl ethers) and vinyl styrene are preferred for the purposes of thepresent invention.

[0053] The compounds containing at least one cationically polymerizablefunctional group which is not an epoxy group suitable for use ascomponent E in accordance with the present invention may contain one orpreferably several cationically polymerizable groups. The compound to beused as component E may be a low molecular weight compound, i.e. acompound with a molecular weight of up to about 400, although arelatively high molecular weight compound with a molecular weight ofabout 400 to about 10,000 or even higher may equally well be used.Component E used in the adhesive to be used in accordance with theinvention may contain only a single compound, although a mixture of twoor more compounds containing cationically polymerizable groups that arenot epoxy groups may equally well be used.

[0054] According to the invention, vinyl ethers are particularlypreferred as component E. Suitable low molecular weight vinyl ethersare, for example, monofunctional and difunctional vinyl ethers. Examplesinclude hydroxy-butyl vinyl ether, triethylene glycol divinyl ether,cyclohexane dimethanol divinyl ether, propylene carbonate propenylether, dodecyl vinyl ether, cyclohexane dimethanol monovinyl ether,cyclohexyl vinyl ether, diethylene glycol divinyl ether, 2-ethylhexylvinyl ether, dipropylene glycol divinyl ether, tripropylene glycoldivinyl ether, hexane diol divinyl ether, octadecyl vinyl ether orbutane diol divinyl ether. Divinyl ethers of higher alcohols may also beused as component E. Examples include glycerol monovinyl ether, glyceroldivinyl ether, glycerol trivinyl ether, trimethylol propane mono-, di-or trivinyl ether, pentaerythritol mono-, di-, tri- or tetravinyl etheror vinyl ethers of alcohols containing more than four OH groups, forexample vinyl ethers of sugar alcohols. The compounds mentioned may beused individually as component E, although component E may equally wellbe a mixture of two or more of the vinyl ethers mentioned.

[0055] According to the invention, butane diol divinyl ether ispreferably used as component E.

[0056] Where a relatively high molecular weight compound is used ascomponent E, the compound in question is preferably a polymer containinga cationically polymerizable group that is not an epoxy group asterminal groups or optionally as lateral groups to the main polymerchain. Compounds such as these, which may preferably be usedindividually or in the form of a mixture of two or more thereof ascomponent E of the adhesive to be used in accordance with the invention,may be obtained, for example, from the relatively high molecular weightpolyol components described as component D in the present specification.For example, a vinyl styrene-terminated polymer may be prepared byreacting an OH-terminated polymer with 4-styrene isocyanate. A polyesterpolyol or polyether polyol or a polyurethane is preferably used as theOH-terminated polymer.

[0057] A broad range of polymers containing vinyl ether groups may alsobe prepared. To this end, an OH-containing polymer, for example, isreacted with an at least two-fold excess of diisocyanates (based on OHgroups). The polymer thus prepared containing free NCO groups is thenreacted with hydroxyvinyl ethers. Polymers containing vinyl ethers mayalso be prepared by initially reacting an OH-containing vinyl ether withan equimolar quantity of a diisocyanate and subsequently reacting thereaction product with an OH-terminated polymer. According to theinvention, preferred OH-containing vinyl ethers are hydroxybutyl vinylether, hydroxyhexyl vinyl ether and cyclohexane dimethanol monovinylether.

[0058] The adhesive to be used in accordance with the inventionpreferably contains component E in a quantity of up to 20% by weight. Inone preferred embodiment, the adhesive to be used in accordance with theinvention contains component E in a quantity of, for example, 0.1% byweight to about 10% by weight, for example in a quantity of about 1 toabout 8% by weight, based on the adhesive as a whole.

[0059] The adhesives to be used in accordance with the invention mayadditionally contain additives including, for example, accelerators,dyes, pigments, fillers, reinforcing agents, thixotropicizing agents,initiators, stabilizers, inhibitors or coupling agents. Accelerators aregenerally used to accelerate the polymerization reaction. This may bedone either by accelerating the initiation reaction taking place underthe effect of radiation or by supporting the polymerization itself, i.e.the addition of the individual monomers onto one another.

[0060] The additives may be present in the adhesive according to theinvention in a total quantity of up to about 20% by weight andpreferably in a total quantity of up to about 10% by weight, for examplein a quantity of about 1% by weight to about 8% by weight or about 3% byweight to about 5% by weight, based on the adhesive as a whole.

[0061] The adhesive compositions according to the invention are normallyprepared by mixing the components mentioned. The resulting mixtures maybe applied to the films to be bonded by machines normally used for suchpurposes, for example by conventional laminating machines. Applicationof the adhesives in liquid form to a film to be bonded to form alaminate is particularly suitable.

[0062] If at least one of the films to be bonded to the surface of thefilm laminate is a transparent film, the adhesive-coated film mayimmediately be laminated with the second film. The film laminate is thentransferred to an irradiation zone where the polymerization reaction,i.e. the crosslinking of the individual adhesive components, isinitiated by exposure of the transparent film side to ultravioletradiation.

[0063] If the films to be bonded together are materials which are nottransparent to polymerization-initiating radiation, the adhesive-coatedfilm generally has to be irradiated on the adhesive side before thatside is bonded to a second film. This procedure presupposes that theadhesive-coated film is applied to the second film at a time when thepolymerization of the adhesive, i.e. the curing process, is still notcomplete. The adhesive must be capable of developing sufficient adhesionat that time for the second web to adhere.

[0064] The described bonding and laminating process may be repeatedseveral times so that laminates consisting of more than two bondedlayers can be produced.

[0065] The bondable materials include, for example, paper, cellulosehydrate, plastics, such as polyethylene, polypropylene, polyethyleneterephthalate, polyvinyl chloride, copolymers of vinyl chloride andvinylidene chloride, copolymers of vinyl acetate olefins, polyamides, ormetal foils, for example of aluminium, lead or copper.

[0066] The following Examples are intended to illustrate the inventionwithout limiting it in any way.

EXAMPLES

[0067] Abbreviations used: PPG: polypropylene glycol Poly-THF:polytetrahydrofuran CAPA: polycaprolactone MDI: 4,4′-diphenyl methanedilsocyanate HBVE: hydroxybutyl vinyl ether

Formulation Example

[0068] PPG  7.1% Aromatic polyester  39.8% Basis cycloaliphat. MDI  8.7%epoxide OH-termin. Cycloaliphatic epoxide  28.9% Use of low CAPA  2.9%molecular weight CAPA Divinyl ether  9.1% and vinyl ether Initiator 3.5% 100.0%

1. The use of an adhesive containing at least three components A, B andC for the production of film laminates, a) component A containing acompound bearing at least one epoxy group, b) component B containing acompound with at least three OH groups and a molecular weight below 400and c) component C containing a photoinitiator which initiates apolymerization of components A and B after exposure to light with awavelength of 100 to 600 nm.
 2. The use claimed in claim 1,characterized in that the adhesive contains a component D, d) componentD being a compound with at least two OH groups and a molecular weight ofat least
 400. 3. The use claimed in claim 1 or 2, characterized in thatcomponent A has a molecular weight of less than
 400. 4. The use claimedin claim 1 or 2, characterized in that component A has a molecularweight of more than
 400. 5. The use claimed in any of the precedingclaims, characterized in that an alcohol containing 3 to 6 OH groups ispresent as component B.
 6. The use claimed in any of the precedingclaims, characterized in that an alcohol selected from the groupconsisting of glycerol, triethylol propane, trimethylol propane orpentaerythritol or a mixture of two or more thereof is present ascomponent B.
 7. The use claimed in any of the preceding claims,characterized in that a photoinitiator selected from the groupconsisting of triaryl sulfonium salts or diaryl iodonium salts ispresent as component C.
 8. The use claimed in any of claims 2 to 7,characterized in that a compound selected from the group of polyesterpolyols, polyether polyols, polycarbonate polyols, polyacetal polyols orpolyurethane polyols is present as component D.
 9. The use claimed inany of the preceding claims, characterized in that the adhesive contains1% by weight to 98% by weight of component A, 1% by weight to 10% byweight of component B and 1% by weight to 10% by weight of component C.10. The use claimed in any of the preceding claims, characterized inthat the adhesive contains a component E, e) component E being acompound or a mixture of two or more compounds containing a cationicallypolymerizable functional group that is not an epoxy group.